Flotation of silica

ABSTRACT

Acid salts of a mixture of normal-alkyl primary amines having 5 to 12 successive chain lengths including both odd and even numbered carbon chains of 8 to 22 carbon atoms, the major proportion of the constituents being near the center of the chain length range, are used as collectors in the flotation of silica from iron ores.

United States Patent 1191 Baarson, deceased et' al.

11.1 3,744,629 14 1 July 10, 1973 FLOTATION OF SILICA [75] Inventors:Robert E. Baarson, deceased, late of LaGrange, "L; by W. Richard Impey,administrator, LaGrange, Ill.

[73] Assignee: Akzonalncorporated,Asheville,

May 18, 1971 (Under Rule 47) [21] Appl. No.: 144,663

[22] Filed:

3,059,773 10/1962 Marullo 209/166 3,404,777 l0/l968 Ray 209/166 OTHERPUBLICATIONS Bailey's lndustrial Oils & Fats, Interscience PublishersPrimary ExaminerFrank W. Lutter Assistant ExaminerRobert l-lalfierAttorney-Francis W. Young, David Terry, Jack H. Hall and Craig,Antonelli and Hill 1 71 1 ABSTRACT Acid salts of a mixture ofnormal-alkyl primary amines having 5 to 12 successive chain lengthsincluding both odd and even numbered carbon chains of 8 to 22 carbonatoms, the major proportion of the constituents being near the center ofthe chain length range, are used as collectors in the flotation ofsilica from iron ores.

9 Claims, No Drawings This invention relates to the concentration ofiron minerals by froth flotation using a mixture of water dispersableacid salts of normal-alkyl primary amines having to 12 successive chainlengths of 8 to 22 carbon atoms, the major proportion of the constitentsbeing near the center of the chain length range. Using these flotationagents, we have found it is possible to obtain a higher selectivity ofsilica and thus produce better recovery of the iron than has beenobtained with currently used collecting agents.

In the recovery and concentration of iron minerals from magnetic ornon-magnetic iron ores, it is the undesirable silica and miscellaneouscherts and siliceous materials that are floated away. The desiredconcentrated iron minerals remain. Froth flotation is well known in theart for separating or concentrating minerals from ore. Prior toflotation, the ore is ground, pulped in water, and sometimes, dependingupon the nature of the ore being treated, preconditioned with starch ordextrin which is a depressant for the desired iron portion of the ore.in the flotation step, a collector and a frothing agent are added to theore dispersed in water and air is introduced into the pulp to form afroth, the silica-rich froth being floated away from the desired ironmineral residue, and the step repeated,

usually 3 to 5 times.

Considerable effort has been extended to devise more efficient and moreeconomical methods of operation to effect as complete a separation aspossible and to produce a higher grade iron concentrate with minimumloss of iron, while consuming a minimal amount of amine collector.Various amines have been used in thepast as flotation agents in theseparation of silica from iron ore. For example, US. Pat. No. 3,404,777teaches the use of secondary-alkyl primary amines in the separation ofsilica from iron ore and U.S. Pat. No. 3,363,758 teaches the use of acidsalts of primary aliphatic ether amines as silica collectors in theconcentration of iron. While many of these collectors have beensatisfactorily used, it is always an object to obtain higher gradeconcentrate and higher recovery of iron minerals.

Accordingly, an object of this invention is to use acid salts of amixture of normal-alkyl primary amineshaving 5 to 12 successive chainlengthsincluding both odd and even numbered carbon chains of 8 to 22carbon atoms, the major proportion of the constituents being near thecenter of the chain length range, as collectors in the concentration ofiron by froth flotation processes. Another object is to use suchmaterials as silica collectors in the froth flotation of iron ore.Another object of this invention is to provide' a novel composition ofnormal-alkyl primary amines to provide highly selective collectors ofsilica. Other objects and advantages of this invention will becomeapparent from the following description and claims.

It has now been found that the use of the mixture of the waterdispersable acid salts of normal-alkyl primary amines having 5 to 12successive chain lengths including both odd and even numbered carbonchains of 8 to 22 carbon atoms wherein the major proportion oftheconstituents are located near the center of the chain length range,effect a marked improvement in silica separation from iron ore. Theindividual normal-alkyl primary amines may be represented by theformula:

2 [R-NH ],,".[A]""' wherein R isan alkyl group having 8 to 22 carbonatoms, A is the salt forming anion of an acid, and n is an integar equalto the valence of said an ion. It is not always necessary that the aminebe totally neutralized, in some cases 12 to 50 percent neutralizationrenders the amine water dispersable. It is preferred that the amine be50 to 100 percent neutralized. Suitmajor constituents as C and C Theamines used in this invention are suitably prepared from'synthetic fattyacid mixtures which contain both odd ,and even numbered successive chainlengths.

Synthetic fatty acids are commerically available and are derived fromparaffin waxes by air oxidation. The amines are produced from the acidsby conventional methods. Such mixtures are different from thosepreviously available from natural sources which only contain substantialamounts of even numbered chain lengths. It appears to be a requirementof this invention that the successive odd and even numberedcarbonchainsbe present. 1 i l The process of this invention is carriedout underwell known techniques of froth flotation. In the case of magnetite ore the natural pH is slightly basic and it is generally notnecessary to adjust pH for flotation. When using hematite ore it isusually necessary to adjust the pH to about 9 to ll by addition of abase such as NaOH. Gen-erally used cell speeds and temperaturesaccording to known flotation techniques are suitable.

The concentration of amine salt used is about 0.01 lb. to 2.0 lbs. perton of ore,.the preferred range being about 0.1 to 0.5 lb. per-ton ofore.

EXAMPLE I Magnetite concentrate ore samples were received with anaverage of 10 wt. percent water. The ores were 'thenblended and headsamples taken. Analysis showed that the ore averaged about wt. percentiron by wet analysis and 8.5 to 10 wt. percentsilica by X-raydiffraction. No. sizing studies were undertaken, although the ground oreaveraged percent passing 325 mesh. The orebody varied considerably inits gauge composition but is generally reported to hold about equalamounts of silica and iron silicates as the gangue material. The majoriron silicate minerals and their silica content are as follows:

500 gms. of ore, on a dry basis, was transferred to a 500 gramlaboratory float cell, 1,500 rpm, and diluted to 50 wt. percent solidsusing Chicago tap water (medium hardness) at ambient temperature. Thepulp was agitated 2 minutes to re-pulp. The ore was diluted to floatsolids. With agitation off, one-half of the amount of collector forthree floats indicated in Table I in lbs. per ton was added in a 2.5 wt.percent water solution. Then 0.05 lbs. per ton methylisobutyl carbinolfrother was added. The cell was turned on and the pulp was conditionedfor 15 seconds without aeration. Flotation was carried out for threeminutes with sufficient aeration for the froth to reach the lip of thecell. This floated product is known as the first Rougher Froth. Theunfloated ore was re-pulped to float solids and using the sameprocedure, one-fourth of the amount of collector indicated in Table land 0.025 lbs. per ton of frother were added, followed by conditioningand flotation. This product is known as the second Rougher Froth. Theore is re-pulped to float solids and the second Rougher Frothprocedure'is duplicated to produce the third Rougher Froth. Both thecell content (the iron concentrate) and the three froth products areseparately filtered, dried, weighed and samples are taken for analysisof iron by wet analysis and for silica by X-ray diffraction. Table Ishows analysis of second and third floats.

TABLE I Collector Flotation Concentrate Fe yp Float v lbs/ton RecoveredFe SiO, SFA Cut 1 Acetate"(100% neutralized 2 0.15 86.9 69.42 3.11 30.20 73.5 70.82 1 55 SFA Cut 2 Acetate (100% neutralized) Y 2 0.15 86.269.51 3.09 3 0.20 70.1 70.97 1.45 Comparative N'Sec-alkyl C trimethylenediamine acetate (100% neutralized) 2 0.12 88.8 68.64 4.41 .3 0.16 75.369.99 3.12 N-tridecoxypropyltrimethylene diamine monoacetate (50 kneutralized 2 0.12 74.8 69.7 3.46 3 0.16 57.2 71.0 2.41 N-Tallow AmineAcetate (100% neutralized) 3 0.14 93.2 67.53 v 6.62 N-Coco Amine Acetate(100% I neutralized) 3 0.14 90.4 67 5.54 NOTE: and SFA Cut 1 and SFA Cut2 Amine is a mixture of normal-alkyl chain lengths as follows:

' Percent (nrbon (hnin SFA (ut l SFA Cut 2 C-ll 4.9 C-l 15.3 0.05 CI 116.7 0.1 C-lZ 20.2 0.2 C-l3 20.4 1.5 C-14 14.5 6.7 C-l5 5.4 12.9 C-l61.9 20.6 C-l7 17.5 018 0.7 25.1 C-l9 7.7 C 20 26 C-21 0.5

Percent Tallow Carbon Chain Saturated Unsaturated C 0.1 C 3 0.5 C 29 2 gC 20 44.6

0.8 Coco C, 0.1 C; 5 C 7 C 45 C 17 C 7 c 4 l4 C, 1

EXAMPLE 11 Using magnetite ore as described in Example 1, flotationswere carried out as described in Example 1 using normal single chainlength amine acetates percent neutralized as a flotation agent for threefloats for comparison with the mixtures of alkyl chain lengths accordingto this invention. 1t can be seen in Table 11 that the individual chainlength amine salts did not produce the very satisfactory resultsobtained by use of mixtures of the same chain length'amine salts shownin Example I.

TABLE 11 Collector Flotation Concentrate Type lbs./ton Fe Recovered %Fe%Si0 C Acetate 0.16 78.3 50.5 5.27 'C Acetate 0.16 55.3 27.3 4.11 CAcetate 0.16 41.4 17.5 3.64 C Acetate 0.16 40.6 16.5 3.50 C Acetate 0.1655.5 25.3 3.97 C Acetate 0.16 79.8 52.8 5.48 C Acetate 0.16 82.7 52.25.41 C Acetate 0.16 96.5 91.0 8.21

EXAMPLE lll Hematite ore samples from a Michigan ore body previouslymagnetically separated from magnetite, were subjected to flotation bythe same process as described in Example 1, except that 1 lb./ton 6080percent soluble British Gum (dextrin) and 2% lb./ton NaOH to obtain pHgreater than 9 were added. Results using the While in the foregoingspecification this invention has been described in relation to certainpreferred embodiments thereof, and many details having been set forthfor purpose of illustrationfit will be apparent to those skilled in theart that certain of the details described herein can be variedconsiderably without dcparting from the basic principles of theinvention.

1 claim:

l. A froth flotation process for separating silica from iron ore whichcomprises froth flotation of said ore in an aqueous medium containing amixture of water dispersable acid salts of normal-alkyl primary amineshaving 5 to 12 successive chain lengths including both odd and evennumbered carbon chains of 8 to 22 carbon atoms, the major proportion ofthe constituents being near the center of the chain length range with atleast two of said center chain lengths of said mixture comprisingbetween l2.9 and 25 percent (by weight) each, and, floating the silicafrom said ore. 10

2. The process of claim 1 wherein said amine salts are used in an amountof 0.01 to 2.0 lbs/ton of ore.

3. The process of claim 2 wherein said amine salts are used in an amountof 0.1 to 0.5 lb./ton of ore.

4. The process of claim 1 wherein said salt is an acetate salts.

tite.

7. The process of claim 1 wherein said amine salts are selected from thegroup consisting of mixtures of and chain lengths C through C with majorconstituconstituents as C C and C

2. The process of claim 1 wherein said amine salts are used in an amountof 0.01 to 2.0 lbs./ton of ore.
 3. The process of claim 2 wherein saidamine salts are used in an amount of 0.1 to 0.5 lb./ton of ore.
 4. Theprocess of claim 1 wherein said salt is an acetate salt.
 5. The processof claim 1 wherein said ore is magnetite.
 6. The process of claim 1wherein said ore is hematite.
 7. The process of claim 1 wherein saidamIne salts are selected from the group consisting of mixtures of amineshaving chain lengths C8 through C16 with the major constituents as C12and C13; chain lengths C11 through C22 with major constituents as C17,C18 and C19; and chain lengths C10 through C14 with major constituentsas C11 and C12.
 8. The process of claim 1 wherein said amine salts areselected from the group consisting of mixtures of amines having chainlengths C8 through C16 with the major constituents as C12 and C13. 9.The process of claim 1 wherein said amine salts are selected from thegroup consisting of mixtures of amines having chain lengths C11 throughC22 with major constituents as C17, C18 and C19.